This thread is kinda old, but I think time travel will be possible. Most likely not in our lifetime but definitly possible. Some day scientists will find a powerful enough power source to propel a space ship faster than the speed of light. Just like if Ikeep modding my Civic it will be faster than a Vette. Another problem is the frrail human body, if you watch Ghost in the Shell in the future we will probably have cyberbrain and artificial body, those things can be made to withstand the force of traveling at light speed.

I believe time travel is possible, but we won't see it in our lifetime.